Treatment for dry eye conditions

ABSTRACT

The present invention provides a method for treating dry eye condition in an individual comprising administrating to said individual an amount of A 3  adenosine receptor (A 3 AR) agonist, the amount being effective to ameliorate symptoms of dry eye in the individual. In accordance with one embodiment, the dry eye condition is manifested by one or more opthalmologic clinical symptoms selected from foreign body sensation, burning, itching, irritation, redness, eye pain, blurred vision, degraded vision and excessive tearing. A preferred A 3 RAg in accordance with the invention is N 6 -(3-iodobenzyl)-adenosine-5′-N-methyluronamide (IB-MECA).

FIELD OF THE INVENTION

The invention relates to compounds and methods useful in the treatmentof dry eye conditions.

BACKGROUND OF THE INVENTION

The preocular tear film plays an important role in the maintenance ofcorneal integrity, the protection against infection and the preservationof visual acuity. A healthy tear film preserves the optical clarity andrefractive power, provides lubrication of the ocular surface andprotection from environmental and infectious attacks. These functions,in turn, are critically dependent upon the stability, tonicity and/orcomposition of the tear film structure. Healthy tears contain a complexmixture of proteins such as antimicrobial proteins (lysozyme,lactoferrin) and growth factors and inflammation suppressors, mucinwhich provides viscosity and stability of the tear and electrolytes forproper osmolarity. Alteration, deficiency or absence of the tear filmmay lead to undesired dryness of the corneal epithelium, ulceration andperforation of the cornea, an increased incidence of infectious disease,and ultimately, severe visual impairment and blindness.

The condition of dry eye is often referred to as a syndrome, or adisease; and it is likewise known by a variety of terms.Keratoconjunctivitis sicca (KCS), or more commonly keratitis sicca,refers to any eye with some degree of dryness.

In dry eye the eye becomes dry either because there is abnormally highrate of evaporation of tears or because there is not enough tears beingproduced. The contents of the tear in an eye suffering from dry eye arealtered with lesser concentrations of proteins such as cytokine whichpromotes inflammation. Additionally, soluble mucin is greatly decreaseddue to loss of goblet cells which impacts viscosity of the tear film.Moreover, there is an increase in electrolyte concentration.

Throughout the world, countless individuals suffer from dry eyesyndrome. The abnormalities leading to tear film dysfunction may besubdivided into four general categories: (a) aqueous tear deficiencies,which are most frequently responsible for dry eye states, originate fromlacrimal gland disorders and include autoimmune disease, congenitalalacrima, paralytic hyposecretion or excretory duct obstruction; (b)mucin deficiency, which is observed in various conjunctivalcicatrization conditions, such as Stevens-Johnson syndrome, trachoma,pemphigoid, thermal and chemical burns, as well as hypovitaminosis A;(c) lipid abnormalities, which may occur during eyelid inflammation(e.g. chronic blepharitis); and (d) diminished eyelid function [Holly,F. J., Tear film physiology. Internat. Opthalmol. Clin. 27:2-6 (1987)].

The first line of treatment is usually eye drops, preferablypreservative free, that act as artificial tears. Most artificial tearsare hydrogels that increase the moisture content on the eye surface andgive some temporary relief. These solutions and ointments give sometemporary relief, but do little to arrest or reverse any damagingconditions. A recently introduced artificial tear product is based onCastor oil emulsion (Refresh Endura tears).

In addition, warm moist compresses applied to the skin of the closedeyelids are also used to reduce tear loss due to evaporation.

For more severe cases of dry eye, in which the cornea is inflamed,anti-inflammatory agents, such as topical steroids (in eye drops) aresometimes prescribed. One example includes the combination of castor oilwith cyclosporine (Restasis).

Oral medicine for dry eye is also available. For example, pilocarpine,the active ingredient in Salagen™ or cevimeline, the active ingredientin Evoxac™, are known to stimulate specific receptors in lacrimal glandand cause increased secretion of tears.

Other remedies include punctal plugs and punctal closure (which blockthe tears from flowing down the tear duct into the nose), and foodsupplements, such as the commercially available Flaxseed oil supplement(Omega-3 Supplement, TheraTears).

Adenosine receptors are classified into four major classes: A1, A2a, A2band A3. A3 adenosine receptors belong to the family of the Gi-proteinassociated cell surface receptors. Receptor activation leads to itsinternalization and the subsequent inhibition of adenylyl cyclaseactivity, cAMP formation and protein kinase A (PKA) expression,resulting in the initiation of various signaling pathways. PKA containsa catalytic subunit PKAc which dissociates from the parent molecule uponactivation with cAMP.

SUMMARY OF THE INVENTION

In accordance with a first aspect, the invention provides a method fortreating dry eye condition in an individual comprising administrating tosaid individual an amount of A₃ adenosine receptor (A₃AR) agonist, theamount being effective to ameliorate dry eye symptoms.

According to one embodiment, the invention provides a method fortreating dry eye syndrome in an individual, comprising administrating tosaid individual an A₃ adenosine receptor (A₃AR) agonist. According toanother embodiment, the dry eye condition is Sjogren's syndrome (SS).

In accordance with a second aspect, the invention provides apharmaceutical composition for treating dry eye conditions comprising asactive ingredient an amount of A₃AR agonist and a physiologicallyacceptable carrier, the amount of said A₃AR agonist being effective toameliorate said dry eye conditions.

In accordance with a third aspect, the present invention provides theuse of an A₃AR agonist for the preparation of a pharmaceuticalcomposition for treating dry eye conditions.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Dry eye conditions and syndromes encompass a constellation of diversedisease processes that produce objective clinical signs ofkeratoconjunctivitis sicca (KCS). The classic prototype of the dry eyesyndrome is Sjögren's syndrome, but there are many other causes of KCSincluding cicatrising conjunctival diseases such as trachoma andpemphigoid, non-cicatrising syndromes causing specific dry eye findings,and atypical syndromes such as keratomalacia in which the eye issymptomatically and objectively dry but tear production is paradoxicallynormal.

The main symptom of dry eye is usually a scratchy or sandy feeling as ifsomething is in the eye. Other symptoms may include stinging or burningof the eye; episodes of excess tearing that follow periods of very drysensation; a stringy discharge from the eye; and pain and redness of theeye. Sometimes individuals with dry eye experience heaviness of theeyelids or blurred, changing, or decreased vision, although loss ofvision is uncommon.

Some individuals with dry eye may have tears that run down their cheeks.This is because the eye may be producing less of the lipid and mucinlayers of the tear film, which help keep tears in the eye. When thishappens, tears do not stay in the eye long enough to thoroughly moistenit.

The present invention provides a method for treating dry eye conditions,preferably dry eye syndrome, comprising providing an individualexhibiting one or more dry eye symptoms and signs with an amount of A₃adenosine receptor (A₃AR) agonist, the amount being effective to treatthe dry eye condition.

As appreciated, while the invention is described in the followingdetailed description with reference to the above method, it is to beunderstood that also encompassed within the present invention arecompositions comprising the A₃AR agonist for use in said treatment.

In the context of the present invention the term “dry eye condition”denotes any condition or syndrome which results in the manifestation ofdry eye symptoms. It includes an already existing condition as well aspseudo dry eye conditions, i.e. conditions high predisposition ofdeveloping dry eye syndromes. Dry eye syndrome may be as a result ofanother underlying condition causing dry eye, for example, Sjogren'ssyndrome, menopause or rheumatoid arthritis. Dry eye may also be acomplication of inflammation, e.g. Blepharitis or of a foreign body inthe eye. Yet dry eye may be a result of infection, or a side effect ofmedications, or exposure to toxins, chemicals, or other substances maycause a symptom or condition of dry eye. Dry eye conditions may bemanifested by one or more opthalmologic clinical symptoms as known inthe art. Some non-limiting examples may include foreign body sensation,burning, itching, irritation, redness, eye pain, blurred vision,degraded vision and excessive tearing.

The term “dry eye symptoms” which may be used interchangeably with theterm “dry eye signs” is used herein to denote any sensation or change innormal function or structure of the eye that is experienced by anindividual. A non-limiting list of signs which may be perceived by asubject and be indicative of an dry eye syndrome includes, dry eyefeeling, sandy eye feeling, scratchy eye feeling, burning eye, stingingor itching eye, excessive tearing, eye pain, redness of the eye, blurredvision, degraded vision.

The terms “treating” or “treatment”, and the like are used herein torefer to obtaining a desired pharmacological and physiological effect.The effect may be prophylactic in terms of preventing or partiallypreventing a disease, symptom or condition of dry eye and/or may betherapeutic in terms of a partial or complete cure of a disease,condition, symptom or adverse effect attributed to dry eye syndrome. Theterm “treatment”, as used herein, covers any treatment of a disease in amammal, particularly a human, and includes: (a) preventing dry eyesyndrome from occurring in an individual which may be predisposed todevelop dry eye syndrome but has not yet been diagnosed as having it,i.e., causing the clinical symptoms of dry eye syndrome not to developin a subject that may be predisposed to dry eye syndrome but does notyet experience or display symptoms of dry eye syndrome; (b) inhibitingdry eye syndrome, i.e., arresting or reducing the development of dry eyesyndrome or its clinical symptoms; or (c) relieving dry eye syndrome,i.e., causing regression of dry eye syndrome and/or its symptoms orconditions.

The term “A₃ adenosine receptor agonist” (A₃AR agonist) in the contextof the present invention refers to any molecule capable of specificallybinding to the A₃AR, thereby fully or partially activating saidreceptor. The A₃AR agonist is thus a molecule that exerts its primeeffect through the binding and activation of the A₃AR. This means thatat the doses it is being administered it essentially binds to andactivates only the A₃AR. In a preferred embodiment, an A₃AR agonist hasa binding affinity (K_(i)) to the human A₃AR in the range of less than100 nM, typically less than 50 nM, preferably less than 20 nM, morepreferably less than 10 nM and ideally less than 5 nM. Particularlypreferred are A₃AR agonists that have a K_(i) to the human A₃R of lessthan 2 nM and desirably less than 1 nM.

It should be noted that some A₃AR agonists can also interact with andactivate other receptors with lower affinities (namely a higher Ki). Amolecule will be considered an A₃AR agonist in the context of theinvention (namely a molecule that exerts its prime effect through thebinding and activation A₃AR) if its affinity to the A₃AR is at least 3times (i.e. its Ki to the A₃AR is at least 3 times lower), preferably 10times, desirably 20 times and most preferably at least 50 times largerthan the affinity to any other of the adenosine receptors (i.e. A₁,A_(2a) and A_(2b)).

The affinity of an A₃AR agonist to the human A₃AR as well as itsrelative affinity to the other human adenosine receptors can bedetermined by a number of assays, such as a binding assay. Examples ofbinding assays include providing membranes containing a receptor andmeasuring the ability of the A₃AR agonist to displace a boundradioactive agonist; utilizing cells that display the respective humanadenosine receptor and measuring, in a functional assay, the ability ofthe A₃AR agonist to activate or deactivate, as the case may be,downstream signaling events such as the effect on adenylate cyclasemeasured through increase or decrease of the cAMP level; etc. Clearly,if the administered level of an A₃AR agonist is increased such that itsblood level reaches a level approaching that of the Ki of the A₁, A_(2a)and A_(2b) adenosine receptors, activation of these receptors may occurfollowing such administration, in addition to activation of the A₃AR. AnA₃AR agonist is thus preferably administered at a dose such that theblood level is such so that essentially only the A₃AR will be activated.

The characteristic of some adenosine A₃AR agonists and methods of theirpreparation are described in detail in, inter alia, U.S. Pat. No.5,688,774; U.S. Pat. No. 5,773,423, U.S. Pat. No. 5,573,772, U.S. Pat.No. 5,443,836, U.S. Pat. No. 6,048,865, WO 95/02604, WO 99/20284, WO99/06053, WO 97/27173 and applicant's co-pending patent application Ser.No. 09/700,751 (corresponding to WO 01/19360), all of which areincorporated herein by reference.

The following examples are specified in U.S. Pat. No. 5,688,774 atcolumn 4, lines 67-column 6, line 16; column 5, lines 40-45; column 6,lines 21-42; column 7, lines 1-11; column 7, lines 34-36; and column 7,lines 60-61:

-   N⁶-(3-iodobenzyl)-9-methyladenine;-   N⁶-(3-iodobenzyl)-9-hydroxyethyladenine;-   R-N⁶-(3-iodobenzyl)-9-(2,3-dihydroxypropyl)adenine;-   S-N⁶-(3-iodobenzyl)-9-(2,3-dihydroxypropyl)adenine;-   N⁶-(3-iodobenzyladenin-9-yl)acetic acid;-   N⁶-(3-iodobenzyl)-9-(3-cyanopropyl)adenine;-   2-chloro-N⁶-(3-iodobenzyl)-9-methyladenine;-   2-amino-N⁶-(3-iodobenzyl)-9-methyladenine;-   2-hydrazido-N⁶-(3-iodobenzyl)-9-methyladenine;-   N⁶-(3-iodobenzyl)-2-methylamino-9-methyladenine;-   2-dimethylamino-N⁶-(3-iodobenzyl)-9-methyladenine;-   N⁶-(3-iodobenzyl)-9-methyl-2-propylaminoadenine;-   2-hexylamino-N⁶-(3-iodobenzyl)-9-methyladenine;-   N⁶-(3-iodobenzyl)-2-methoxy-9-methyladenine;-   N⁶-(3-iodobenzyl)-9-methyl-2-methylthioadenine;-   N⁶-(3-iodobenzyl)-9-methyl-2-(4-pyridylthio)adenine;-   (1S,2R,3S,4R)-4-(6-amino-2-phenylethylamino-9H-purin-9-yl)cyclopentane-1,2,3-triol;-   (1S,2R,3S,4R)-4-(6-amino-2-chloro-9H-purin-9-yl)cyclopentane-1,2,3-triol;-   (±)-9-[2α,3α-dihydroxy-4β-(N-methylcarbamoyl)cyclopent-1β-yl]-N⁶-(3-iodobenzyl)-adenine;-   2-chloro-9-(2′-amino-2′,3′-dideoxy-β-D-5′-methyl-arabino-furonamido)-N⁶-(3-iodobenzyl)adenine;-   2-chloro-9-(2′,3′-dideoxy-2′-fluoro-β-D-5′-methyl-arabino    furonamido)-N⁶-(3-iodobenzyl)adenine;-   9-(2-acetyl-3-deoxy-β-D-5-methyl-ribofuronamido)-2-chloro-N⁶-(3-iodobenzyl)adenine;-   2-chloro-9-(3-deoxy-2-methanesulfonyl-β-D-5-methyl-ribofuronamido)-N⁶-(3-iodobenzyl)adenine;-   2-chloro-9-(3-deoxy-β-D-5-methyl-ribofuronamido)-N⁶-(3-iodobenzyl)adenine;-   2-chloro-9-(3,5-1,1,3,3-tetraisopropyldisiloxyl-β-D-5-ribofuranosyl)-N⁶-(3-iodobenzyl)adenine;-   2-chloro-9-(2′,3′-0-thiocarbonyl-β-D-5-methyl-ribofuronamido)-N⁶-(3-iodobenzyl)adenine;-   9-(2-phenoxythiocarbonyl-3-deoxy-β-D-5-methyl-ribofuronamido)-2-chloro-N⁶-(3-iodobenzyl)adenine;-   1-(6-benzylamino-9H-purin-9-yl)-1-deoxy-N,4-dimethyl-β-D-ribofuranosiduronamide;-   2-chloro-9-(2,3-dideoxy-β-D-5-methyl-ribofuronamido)-N⁶    benzyladenine;-   2-chloro-9-(2′-azido-2′,3′-dideoxy-β-D-5′-methyl-arabino-furonamido)-N⁶-benzyladenine;-   2-chloro-9-(β-D-erythrofuranoside)-N⁶-(3-iodobenzyl)adenine;-   N⁶-(benzodioxanemethyl)adenosine;-   1-(6-furfurylamino-9H-purin-9-yl)-1-deoxy-N-methyl-β-D-ribofuranosiduronamide;-   N⁶-[3-(L-prolylamino)benzyl]adenosine-5′-N-methyluronamide;-   N⁶-[3-(β-alanylamino)benzyl]adenosine-5′-N-methyluronamide;-   N⁶-[3-(N-T-Boc-β-alanylamino)benzyl]adenosine-5′-N-methyluronamide-   6-(N′-phenylhydrazinyl)purine-9-β-ribofuranoside-5′-N-methyluronamide;-   6-(O-phenylhydroxylamino)purine-9-β-ribofuranoside-5′-N-methyluronamide;-   9-(β-D-2′,3′-dideoxyerythrofuranosyl)-N⁶-[(3-β-alanylamino)benzyl]adenosine;-   9-(β3-D-erythrofuranoside)-2-methylamino-N⁶-(3-iodobenzyl)adenine;-   2-chloro-N-(3-iodobenzyl)-9-(2-tetrahydrofuryl)-9H-purin-6-amine;-   2-chloro-(2′-deoxy-6′-thio-L-arabinosyl)adenine; and-   2-chloro-(6′-thio-L-arabinosyl)adenine

In U.S. Pat. No. 5,773,423 at column 6, line 39, to column 7, line 14,specifically disclosed are compounds which include the formula:

wherein

X₁ is R^(a)R^(b)NC(═O), wherein R^(a) and R^(b) may be the same ordifferent and are selected from the group consisting of hydrogen, C₁-C₁₀alkyl, amino, C₁-C₁₀ haloalkyl, C₁-C₁₀ aminoalkyl, and C₃-C₁₀cycloalkyl;

R₂ is selected from the group consisting of hydrogen, halo, C₁-C₁₀alkyoxy, amino, C₂-C₁₀ alkenyl, and C₂-C₁₀ alkynyl; and

R₅ is selected from the group consisting of R- and S-1-phenylethyl, anunsubstituted benzyl group, and a benzyl group substituted in one ormore positions with a substituent selected from the group consisting ofC₁-C₁₀ alkyl, amino, halo, C₁-C₁₀ haloalkyl, nitro, hydroxy, acetamido,C₁-C₁₀ alkoxy, and sulfo.

More specific compounds include those of the above formula wherein R^(a)and R^(b) may be the same or different and are selected from the groupconsisting of hydrogen and C₁-C₁₀ alkyl, particularly when R₂ ishydrogen or halo, especially hydrogen.

Additional specific compounds are those compounds wherein R^(a) ishydrogen and R₂ is hydrogen, particularly when R₅ is unsubstitutedbenzyl.

More specific compounds are such compounds wherein R^(b) is a C₁-C₁₀alkyl or C₃-C₁₀ cycloalkyl, particularly a C₁-C₁₀ alkyl, and moreparticularly methyl.

Especially specific are those compounds where R^(a) is hydrogen, R^(b)is C₁-C₁₀ alkyl or C₃-C₁₀ cycloalkyl, and R₅ is R- or S-1-phenylethyl ora benzyl substituted in one or more positions with a substituentselected from the group consisting of halo, amino, acetamido, C₁-C₁₀haloalkyl, and sulfo, where the sulfo derivative is a salt, such as atriethylammonium salt.

An example of an especially preferred compound disclosed in U.S. Pat.No. 5,773,423 is IB-MECA. In addition, those compounds in which R₂ is aC₂-C₁₀ alkenylene of the formula R^(d)—C═C— where R^(d) is a C₁-C₈ alkylare particularly noted in this publication. Also specific are thosecompounds wherein R₂ is other than hydrogen, particularly those whereinR₂ is halo, C₁-C₁₀ alkylamino, or C₁-C₁₀ alkylthio, and, morepreferably, when additionally R^(a) is hydrogen, R^(b) is a C₁-C₁₀alkyl, and/or R₅ is a substituted benzyl.

Such specifically disclosed compounds include2-chloro-N⁶-(3-iodobenzyl)-9-[5-(methylamido)-β-D-ribofuranosyl]-adenine,N⁶-(3-iodobenzyl)-2-methylamino-9-[5-(methylamido)-β-D-ribofuranosyl]-adenine,andN⁶-(3-iodobenzyl)-2-methylthio-9-[5-(methylamido)-β-D-ribofuranosyl]-adenine

Further U.S. Pat. No. 5,773,423 discloses at column 7, line 60, throughcolumn 8, line 6, A₃AR agonists as modified xanthine-7-ribosides havingthe formula:

wherein

X is O;

R₆ is R^(a)R^(b)NC(═O), wherein R^(a) and R^(b) may be the same ordifferent and are selected from the group consisting of hydrogen, C₁-C₁₀alkyl, amino, C₁-C₁₀ haloalkyl, C₁-C₁₀ aminoalkyl, and C₃-C₁₀cycloalkyl;

R₇ and R₈ may be the same or different and are selected from the groupconsisting of C₁-C₁₀ alkyl, R- and S-1-phenylethyl, an unsubstitutedbenzyl group, and a benzyl group substituted in one or more positionswith a substituent selected from the group consisting of C₁-C₁₀ alkyl,amino, halo, C₁-C₁₀ haloalkyl, nitro, hydroxy, acetamido, C₁-C₁₀ alkoxy,and sulfo; and

R₉ is selected from the group consisting of halo, benzyl, phenyl, andC₃-C₁₀ cycloalkyl.

-   WO 99/06053 discloses in examples 19-33 compounds selected from:-   N⁶-(4-biphenyl-carbonylamino)-adenosine-5′-N-ethyluronamide;-   N⁶-(2,4-dichlorobenzyl-carbonylamino)-adenosine-5′-N-ethyluronamide;-   N⁶-(4-methoxyphenyl-carbonylamino)-adenosine-5′-N-ethyluronamide;-   N⁶-(4-chlorophenyl-carbonylamino)-adenosine-5′-N-ethyluronamide;-   N⁶-(phenyl-carbonylamino)-adenosine-5′-N-ethyluronamide;-   N⁶-(benzylcarbamoylamino)-adenosine-5′-N-ethyluronamide;-   N⁶-(4-sulfonamido-phenylcarbamoyl)-adenosine-5′-N-ethyluronamide;-   N⁶-(4-acetyl-phenylcarbamoyl)-adenosine-5′-N-ethyluronamide;-   N⁶-((R)-α-phenylethylcarbamoyl)-adenosine-5′-N-ethyluronamide;-   N⁶-((S)-α-phenylethylcarbamoyl)-adenosine-5′-N-ethyluronamide;-   N⁶-(5-methyl-isoxazol-3-yl-carbamoyl)-adenosine-5′-N-ethyluronamide;-   N⁶-(1,3,4-thiadiazol-2-yl-carbamoyl)-adenosine-5′-N-ethyluronamide;-   N⁶-(4-n-propoxy-phenylcarbamoyl)-adenosine-5′-N-ethyluronamide;-   N⁶-bis-(4-nitrophenylcarbamoyl)-adenosine-5′-N-ethyluronamide; and-   N⁶-bis-(5-chloro-pyridin-2-yl-carbamoyl)-adenosine-5′-N-ethyluronamide.

According to one embodiment of the invention, the A₃AR agonist is acompound that exerts its prime effect through the binding and activationof the adenosine A₃AR and is a purine derivative falling within thescope of the general formula (I):

wherein,

-   -   R₁₁ represents an alkyl, hydroxyalkyl, carboxyalkyl or        cyanoalkyl or a group of the following general formula (II):

in which:

-   -   Y represents oxygen, sulfur or CH₂;    -   X₁₁ represents H, alkyl, R^(e)R^(f)NC(═O)— or HOR^(g)—, wherein        -   R^(e) and R^(f) may be the same or different and are            selected from the group consisting of hydrogen, alkyl,            amino, haloalkyl, aminoalkyl, BOC-aminoalkyl, and cycloalkyl            or are joined together to form a heterocyclic ring            containing two to five carbon atoms; and        -   R^(g) is selected from the group consisting of alkyl, amino,            haloalkyl, aminoalkyl, BOC-aminoalkyl, and cycloalkyl;    -   X₁₂ is H, hydroxyl, alkylamino, alkylamido or hydroxyalkyl;    -   X₁₃ and X₁₄ represent independently hydrogen, hydroxyl, amino,        amido, azido, halo, alkyl, alkoxy, carboxy, nitrilo, nitro,        trifluoro, aryl, alkaryl, thio, thioester, thioether, —OCOPh,        —OC(═S)OPh or both X₁₃ and X₁₄ are oxygens connected to >C═S to        form a 5-membered ring, or X₁₂ and X₁₃ form the ring of formula        (III):

where R′ and R″ represent independently an alkyl group;

-   -   R₁₂ is selected from the group consisting of hydrogen, halo,        alkylether, amino, hydrazido, alkylamino, alkoxy, thioalkoxy,        pyridylthio, alkenyl; alkynyl, thio, and alkylthio; and    -   R₁₃ is a group of the formula —NR₁₅R₁₆ wherein    -   R₁₅ is a hydrogen atom or a group selected from alkyl,        substituted alkyl or aryl-NH—C(Z)—, with Z being O, S, or NR^(a)        with R^(e) having the above meanings; wherein when R₁₅ is        hydrogen than    -   R₁₆ is selected from the group consisting of R- and        S-1-phenylethyl, benzyl, phenylethyl or anilide groups        unsubstituted or substituted in one or more positions with a        substituent selected from the group consisting of alkyl, amino,        halo, haloalkyl, nitro, hydroxyl, acetoamido, alkoxy, and        sulfonic acid or a salt thereof; benzodioxanemethyl, fururyl,        L-propylalanyl-aminobenzyl, β-alanylamino-benzyl,        T-BOC-β-alanylaminobenzyl, phenylamino, carbamoyl, phenoxy or        cycloalkyl; or R₁₆ is a group of the following formula:

or when R₁₅ is an alkyl or aryl-NH—C(Z)—, then, R₁₆ is selected from thegroup consisting of heteroaryl-NR^(a)—C(Z)—, heteroaryl-C(Z)—,alkaryl-NR^(a)—C(Z)—, alkaryl-C(Z)—, aryl-NR—C(Z)— and aryl-C(Z)—; Zrepresenting an oxygen, sulfor or amine; or a physiologically acceptablesalt of the above compound.

According to one preferred embodiment, the A₃AR agonist is a nucleosidederivative of the general formula (IV):

wherein X₁, R₂′ and R₅ are as defined above, and physiologicallyacceptable salts of said compound.

The non-cyclic carbohydrate groups (e.g. alkyl, alkenyl, alkynyl,alkoxy, aralkyl, alkaryl, alkylamine, etc) forming part of thesubstituent of the compounds of the present invention are eitherbranched or unbranched, preferably containing from one or two to twelvecarbon atoms.

When referring to “physiologically acceptable salts” of the compoundsemployed by the present invention it is meant any non-toxic alkalimetal, alkaline earth metal, and ammonium salt commonly used in thepharmaceutical industry, including the sodium, potassium, lithium,calcium, magnesium, barium ammonium and protamine zinc salts, which areprepared by methods known in the art. The term also includes non-toxicacid addition salts, which are generally prepared by reacting thecompounds of this invention with a suitable organic or inorganic acid.The acid addition salts are those which retain the biologicaleffectiveness and qualitative properties of the free bases and which arenot toxic or otherwise undesirable. Examples include, inter alia, acidsderived from mineral acids, hydrochloric, hydrobromic, sulfuric, nitric,phosphoric, metaphosphoric and the like. Organic acids include, interalia, tartaric, acetic, propionic, citric, malic, malonic, lactic,fumaric, benzoic, cinnamic, mandelic, glycolic, gluconic, pyruvic,succinic salicylic and arylsulphonic, e.g. p-toluenesulphonic, acids.

Specific examples of A₃AR agonist which may be employed according togeneral formula (IV) of the present invention include, without beinglimited thereto, N⁶-2-(4-aminophenyl)ethyladenosine (APNEA),N⁶-(4-amino-3-iodobenzyl) adenosine-5′-(N-methyluronamide) (AB-MECA),N⁶-(3-iodobenzyl)-adenosine-5′-N-methyluronamide (IB-MECA) and2-chloro-N⁶-(3-iodobenzyl)-adenosine-5′-N-methyluronamide (Cl-IB-MECA).IB-MECA is the most preferred compound in accordance with the invention.

According to another embodiment, the A₃AR agonist may be an oxidederivative of adenosine, such asN⁶-benzyladenosine-5′-N-alkyluronamide-N¹-oxide orN⁶-benzyladenosine-5′-N-dialkyluronamide-N¹-oxide, wherein the 2-purineposition may be substituted with an alkoxy, amino, alkenyl, alkynyl orhalogen.

The terms “effective amount” or “amount effective to” in the context ofthe present invention refer to an amount of A₃AR agonist which preventsor reduces symptoms of dry eye in patients. The “effective amount” canbe readily determined, in accordance with the invention, byadministering to a plurality of tested subjects various amounts of theA₃AR agonist and then plotting the physiological response (for examplean integrated “SS index” combining several of the therapeuticallybeneficial effects) as a function of the amount. Alternatively, theeffective amount may also be determined, at times, through experimentsperformed in appropriate animal models and then extrapolating to humanbeings using one of a plurality of conversion methods; or by measuringthe plasma concentration or the area under the curve (AUC) of the plasmaconcentration over time and calculating the effective dose so as toyield a comparable plasma concentration or AUC. As known, the effectiveamount may depend on a variety of factors such as mode of administration(for example, oral administration may require a higher dose to achieve agiven plasma level or AUC than an intravenous administration); the age,weight, body surface area, gender, health condition and genetic factorsof the subject; other administered drugs; etc.

In the following, unless otherwise indicated, dosages are indicated inweight/Kg, meaning weight of administered A₃AR agonist (e.g. IB-MECA)per kilogram of body weight of the treated subject in eachadministration. For example, mg/Kg and microgram/Kg denote,respectively, milligrams of administered agent and micrograms ofadministered agent per kilogram of body weight of the treated subject.

The effective amount is preferably less than about 1 mg/kg body weight,particularly less than about 500 μg/kg or even less than about 200 μg/kgbody weight or at times less than about 100 μg/kg body weight or evenless than about less than 50 μg/kg body weight. With respect to IB-MECA,the effective amount is preferably less than 5 mg each dose, for oncedaily administration (namely a dose less than about 70 μg/kg bodyweight, assuming an average individual weight of about 70 kg), and lessthan about 4 mg each dose (i.e. less than about 57 μg/kg body weight),for twice daily administration. The dose of IB-MECA is more preferablyless than about 2 mg each dose and typically between about 0.1-1 mg eachdose, for either once or twice daily administration (the correspondingdosages in weight per body weight being about 29 μg/kg and about 1.5-15μg/kg body weight, respectively).

The administration of the A₃AR agonist to an individual may be togetherwith a pharmaceutically acceptable carrier. In the case where theadministration is oral, the carrier is one that is acceptable for oraladministration. In the case where the administration is topical, thecarrier is one that is acceptable for topical administration, oneexample being ocular administration.

By the term “pharmaceutically acceptable carrier” it is meant any one ofinert, non-toxic materials, which do not react with the A₃AR agonist andwhich can be added to formulations as diluents or carriers or to giveform or consistency to the formulation.

An oral formulation may be in the form of a pill, capsule, in the formof a syrup, an aromatic powder, and other various forms. The carrier isselected at times based on the desired form of the formulation. Thecarrier may also at times have the effect of the improving the deliveryor penetration of the active ingredient to the target tissue, forimproving the stability of the drug, for slowing clearance rates, forimparting slow release properties, for reducing undesired side effectsetc. The carrier may also be a substance that stabilizes the formulation(e.g. a preservative), for providing the formulation with an edibleflavor, etc. The carriers may be any of those conventionally used and islimited only by chemical-physical considerations, such as solubility andlack of reactivity with the A₃AR agonist, and by the route ofadministration. The carrier may include additives, colorants, diluents,buffering agents, disintegrating agents, moistening agents,preservatives, flavoring agents, and pharmacologically compatiblecarriers. In addition, the carrier may be an adjuvant, which, bydefinition are substances affecting the action of the active ingredientin a predictable way.

Typical examples of carriers suitable for oral administration comprise(a) liquid solutions, where an effective amount of the active substanceis dissolved in diluents, such as water, saline, natural juices,alcohols, syrups, etc.; (b) capsules (e.g. the ordinary hard- orsoft-shelled gelatin type containing, for example, surfactants,lubricants, and inert fillers), tablets, lozenges (wherein the activesubstance is in a flavor, such as sucrose and acacia or tragacanth orthe active substance is in an inert base, such as gelatin and glycerin),and troches, each containing a predetermined amount of the tragacanth assolids or granules; (c) powders; (d) suspensions in an appropriateliquid; (e) suitable emulsions; (f) liposome formulation; and others.

A topical formulation may be in any form suitable for topicaladministration, including, without being limited thereto, an ophthalmicsolution (e.g. eye drops), an ophthalmic gel or an ophthalmic ointmentor oily lotion. Topical administration of the A₃AR agonist alsocomprises the use of ophthalmic patches carrying the A₃AR agonist in asuitable drug containing layer and to be placed on top of the eyelid aswell as to Ocular inserts which are devices containing the A₃AR agonistand placed into the inferior or superior conjunctival sacs (see forexample WO0059420).

Eye drops may be prepared by dissolving A₃AR agonist in a sterileaqueous solution such as saline, buffering solution etc., or bycombining powder compositions to be dissolved before use. Otheradditives may be included in the eye drops such as isotonizing agents(e.g., sodium chloride, etc.), buffer agent (e.g., boric acid, sodiummonohydrogen phosphate, sodium dihydrogen phosphate, etc.),preservatives (e.g., benzalkonium chloride, benzethonium chloride,chlorobutanol, etc.), thickeners (e.g., saccharide such as lactose,mahnitol, maltose, etc.; e.g., hyaluronic acid or its salt such assodium hyaluronate, potassium hyaluronate, etc.; e.g.,mucopolysaccharide such as chondroitin sulfate, etc.; e.g., sodiumpolyacrylate, carboxyvinyl polymer, crosslinked polyacrylate, etc.).

Eye ointments may be prepared by mixing A3AR agonist into a base.Examples of the base for eye ointment include petrolatum, selen 50,Plastibase, macrogol, etc., but not limited thereto.

Some exemplary ophthalmic viscosity enhancers that can be used in thepresent formulation include: carboxymethyl cellulose sodium;methylcellulose; hydroxypropyl cellulose; hydroxypropylmethyl cellulose;hydroxyethyl cellulose; polyethylene glycol 300; polyethylene glycol400; polyvinyl alcohol; and providone.

Some natural products, such as veegum, alginates, xanthan gum, gelatin,acacia and tragacanth, may also be used to increase the viscosity ofophthalmic solutions.

A tonicity is important because hypotonic eye drops cause an edema ofthe cornea, and hypertonic eye drops cause deformation of the cornea.The ideal tonicity is approximately 300 mOsM. The tonicity can beachieved by methods described in Remington: The Science and Practice ofPharmacy, known to those versed in the art.

As used herein, the forms “a”, “an” and “the” include singular as wellas plural references unless the context clearly dictates otherwise. Forexample, the term “an A₃AR agonist” includes one or more compounds whichare capable of specifically binding to the A₃AR, thereby fully orpartially activating said receptor.

Further, as used herein, the term “comprising” is intended to mean thatthe composition include the recited active agent, i.e. A₃AR agonist, butnot excluding other elements, such as physiologically acceptablecarriers and excipients as well as other active agents. The term“consisting essentially of” is used to define compositions which includethe recited elements but exclude other elements that may have anessential significance on treatment of dry eye syndrome. “Consisting of”shall thus mean excluding more than trace elements of other elements.Embodiments defined by each of these transition terms are within thescope of this invention.

Further, all numerical values, e.g. when referring the amounts or rangesof the elements constituting the composition comprising the A₃AR agonistas an active ingredient, are approximations which are varied (+) or (−)by up to 20%, at times by up to 10% of from the stated values. It is tobe understood, even if not always explicitly stated that all numericaldesignations are preceded by the term “about”.

The invention will now be exemplified in the following description ofexperiments that were carried out in accordance with the invention. Itis to be understood that these examples are intended to be in the natureof illustration rather than of limitation. Obviously, many modificationsand variations of these examples are possible in light of the aboveteaching. It is therefore, to be understood that within the scope of theappended claims, the invention may be practiced otherwise, in a myriadof possible ways, than as specifically described hereinbelow.

Some Non-Limiting Examples IB-MECA Improves Dry Eye Symptoms inRheumatoid Arthritis Patients Drug:

The A₃AR agonist used was a clinical grade of the compound knowngenerically as1-Deoxy-1-[6-[[(3-iodophenyl)methyl]amino]-9H-purine-9-yl]-N-methyl-D-ribofuranuronamideor as N⁶-(3-iodobenzyl)-adenosine-5′-N-methyluronamide (IB-MECA), thatwas synthesized for Can-Fite BioPharma, under good clinical practice(GMP) by Albany Molecular Research Inc, Albany, N.Y., USA.

The IB-MECA was formulated in oval softgel capsules. The capsulescontained solutions of IB-MECA in Cremophor RH 40 and Miglyol 812. Thecapsules contained a dose of 0.1, 1 or 4 mg of IB-MECA, the exactcomposition of each capsules' type is shown in the following Tables 1-3:

TABLE 1 Composition of 0.1 mg IB-MECA Softgel Capsules IngredientCapsule % W/W IB-MECA  0.105 mg 0.021 Polyoxyl 45 Castor Oil, 326.495 mg65.299 USP (Cremophor RH 40) Miglyol 812 173.400 mg 34.680

TABLE 2 Composition of 1 mg IB-MECA Softgel Capsules Ingredient Capsule% W/W IB-MECA   1.05 mg 0.210 Polyoxyl 45 Castor Oil, 325.975 mg 65.195USP (Cremophor RH 40) Miglyol 812 172.975 mg 34.595

TABLE 3 Composition of 4 mg IB-MECA Softgel Capsules Ingredient Capsule% W/W IB-MECA  4.2 mg 0.84 Polyoxyl 45 Castor Oil, 324.4 mg 64.88 USP(Cremophor RH 40) Miglyol 812 171.4 mg 34.28

Methods:

The capsules with IB-MECA were given to patients orally twice daily. Allpatients had rheumatoid arthritis (RA) and were give IB-MECA within theframework of a clinical study aimed at testing the effect of IB-MECA inmodifying RA disease symptoms in these patients. The patients receivedrandomly capsules of one of the above there doses. The patients receivedthe IB-MECA for a period of 12 weeks.

4 out of the treated patients also suffered from Sicca and the effect ofIB-MECA on their dry eye symptoms was examined as well.

Results

Table 4 summarizes the results of IB-MECA treatment of RA patients.Specifically, four patients at the age 58±4 years who suffered from RAfor 8±2 years were followed. At base line, the patients had elevatedlevels of rheumatoid factor, i.e., 313±120 IU/ml (0<normal<40) and hadsuffered from dry eyes for 5±1.6 years. Upon treatment with IB-MECA for6.25±1.1 months, an improvement in Schirmer's test from 8.5±1.4 mm to15.6±2.9 mm was observed.

TABLE 4 Effect of IB-MECA treatment (twice daily) on RA patientsSchirmer test RA Dry eye Period of Left eye Right eye Age durationduration Hepatitis treatment End of End of Patient Dose (years) (years)(years) C Virus (month) Base line study Base line study 1 0.1 65 14 5positive 4 6 9 14 9 2 1.0 58 7 7 positive 5 10 32 15 23 3 4.0 54 6 5 7 516 5 17 4 1.0 70 5 3 9 6 9 7 10 Mean 61.75 8.00 5 6.25 6.75 16.5 10.2514.75 SE 2.4 0.51 0.82 1.11 1.11 5.4 2.5 3.28

Treatment of Secondary Sjogren Syndrome Symptoms in Rheumatoid ArthritisPatients

A patient with rheumatoid arthritis (RA) and secondary Sjogren symptoms,mainly manifested by dry eye, treated for years with eye drops (tearsubstitutes) participated in a phase 2 clinical trial with IB-MECA forthe treatment of active RA. The patient's symptoms of dry eye wereimproved significantly, to the extent of discontinuation of the use oftear substitutes.

Methods

The patient took part in a phase 2, multicenter, randomized,double-blind, parallel-group, dose-ranging study of the safety andpreliminary efficacy of daily IB-MECA administered orally for 12 weeksto patients with active rheumatoid arthritis.

The patient is a 53 years old female with a 7 year history of RA,previously treated with 3 disease-modifying anti-rheumatic drugs(DMARDs), and a history of 2-3 years of dry eyes treated with tearsubstitutes a few times a day. After a 4 week DMARD washout period, thepatient was treated with a blinded dose of IB-MECA—either 0.1, 1.0 or4.0 mg q12 h for 12 weeks. She is currently continuing IB-MECA treatmentunder a long term extension protocol of the original 12 weeks study.

Results

There had been a marked improvement in the condition of the RA in thispatient, represented by objective measurements of swollen and tenderjoints, acute phase reactants (ESR and CRP), patient and physicianglobal assessments, patient assessment of pain and disability. Althoughthe evaluation of secondary Sjogren's symptoms had not been a part ofthe patient evaluation in this study, the patient reported that afteryears of continuous use of tear substitutes for dry eye, after about 3-4weeks of IB-MECA administration she did not need them any more, and shecurrently has no symptoms of dry eye.

CONCLUSION

Treatment with IB-MECA resulted in a substantial improvement of the dryeye symptoms of secondary Sjogren's syndrome in a patient with activeRA.

1.-10. (canceled)
 11. A method for treating a dry eye condition in anindividual, comprising administering to the individual in need thereof,an amount of an A₃AR agonist effective to ameliorate symptoms of dry eyein the individual, wherein the A₃AR agonist binds to and activates theA₃AR.
 12. The method of claim 11, wherein the dry eye condition is a dryeye syndrome.
 13. The method of claim 11, wherein the dry eye conditionis secondary Sjögren's syndrome.
 14. The method of claim 11, wherein theA₃AR agonist is orally administered.
 15. The method of claim 14, whereinthe A₃AR agonist is orally administered twice a day.